Temperature control for driers and other heat exchange elements



July 28, 1942. A. E. ARMSTRONG 2,291,131 TEMPERATURE CONTROL FOR DRIERS AND OTHER HEAT EXCHANGE ELEMENTS 2 Sheet s-Sh eet 1 Filed Aug. 19, 1940 y 1942- A. E. ARMSTRONG 2,291,131

TEMPERATURE CONTROL FOR DRIERS AND OTHER HEAT EXCHANGE ELEMENTS Filed Aug. 19, 1940 2 Sheets-Sheet 2 INVENTOR. I Ada/l2 Z. /4/"/77J//'0// BY c l mi rfiw A ORNEYS Patented July 28, 1942 TEMPERATURE CONTROL FOR DRIER/S AND OTHER HEAT EXCHANGE ELEMENTS Adam E. Armstrong, Three Rivers, Mich., assignor to Armstrong Machine Vtorks, Three Rivers,

Mich., a corporation of Michigan Application August 19 1940, Serial No. 353,270

24 Claims.

This invention relates to improvements in temperature controls for driers and other heat exchange elements.

The main objects of this invention are:

First, to provide a control for low temperature broken away and in vertical section illustrating paper driers, cotton slashers, and the like, which details of construction of the control of Fig. 5. is suitable for installation on individual -driers In paper drying machines, it is desirable that to control and maintain the temperature thereof. the initial or wet end driers be held at low tem- Second, to provide a control of the type deperature and that the heat radiated from these scribed adapted to maintain a very. uniform driers be maintained approximately constant. .If Y temperature in low pressure driers of the above a condition of uniform heat radiation is mainstated type and in association with means for tained at the wet end of the machine, it will be removing condensate therefrom. apparent that the task of maintaining control of Third, to provide a control of the type dethe drying conditions at the subsequent or dry scribed adapted to accurately regulate the temend of the machine is facilitated. The device of perature of a drying cylinder adjacent the pethis invention-is accordingly intended to serve riphery thereof, the said control effecting its this purpose, although my invention has awide functions without error arising because of differrange of uses and applications. In its preferred ences in temperature within the drier. embodiment, I contemplate that a control device Fourth, to provide a control of the, type dein accordance with the description tofollow shall scribed for a number of drying cylinders which be supplied for each of the wet end driers of which are to be operated at different or graduated temthere are usually only afew, so that the temperatures and including means for simultaneperature of these driers may be individually set ously adjusting the temperature of the cylinders and continually maintained at the originalsetwhile maintaining the graduated relation thereof. ting thereof,

Fifth, to provide a novel method of controlling Referring to the drawings, the reference nua steam heated drying unit. meral l indicates the cylindrical drying element Objects relatingto details and economies of or cylinder of a paper drying machine, which in the invention will appear from the description to accordance withone conte p ted ad ptation. of follow. The invention is defined in the claims. the inventionis located at the wet end or web A'structure embodying the features of my ininput end of the machine, although it will'appear vention is illustrated in the accompanying drawfrom, the description to follow that the invention ings, wherein: V is not unduly restricted as to the location of the Fig. l is a view illustrating conventionally a cylinder or shell to which it is applied in the drydrier element of a web drying machine, cotton 5 ing machine or in its various applications: and slasher, or like heat exchanger, the same being uses. I shown partially in longitudinal section with ele- The reference numeral 2 designates a pipe supments of my improved control shown in operap y Steam t0 t Cylinder, in Which p is fi l ti thereto, inserted a non-return check valve 3. A suitable Fig. 2 is a somewhat enlarged view partially 40 pressure regulator 4 is provided in the steam line broken away and in section on line 2-2 of Fig. for assuring a constant S m P s e- 1, illustrating details of construction of the con- In communication with the steam line on the trol. down stream side of the check valve 3 is a tube Fig. .3 is a fragmentary view in section on line or connection 5 for supplying air for mixture 3-3 of Fig. 1. 5 with steam enteringthe cylinder, the flow of air temperatures when desired while maintaining said relation.

Fig. 5' is a view partially broken away and in longitudinal section illustrating a modified emvbodiment of control in accordance with my invention shown in operative relation to a drier element.

Fig. 6 is a somewhat enlarged view partially being controlled by a valve in the air connection which is generally designated 6. The air pressure is preferably slightly in excess of the steam pressure. The cylinder is provided with a hollow journal assembly conventionally illustrated and generally designated 1, through which the mixture of steam is admitted to its interior. Extending through this journal is an air and condensate discharge pipe 8 of the siphon type having a downturned' end 9 terminating closely adby one of 2 iacent the periphery of the cylinder. This pipe discharges in a chamber ill in the journal assembly and from there through a pipe H to an air and steam exhaust tube or connection l2 and a further pipe I 3 leading to a steam trap I for discharging condensate. The air and steam discharge tube I2 is controlled byfa valve which is generally designated IS, the air inlet valve 6 and the steam and air discharge valve l5 being automatically operated'in accordance with the temperature adjacent the innerperiphery of cylinder I in a manner to be described.

Disposed between and secured to the valves 6,

the total pressure exerted by a mixture of gases is equal to the sum of the separate pressures which each gas would exert if it alone occupied the whole volume filled by the mixture. When pure saturated steam exists within a chamber, the temperature of the steam definitely depends on. its pressure, and the pressure being known,

I5 are a pair of rectangular frame members l6 which are secured as by screws to a pair of trans verse bellows abutment members l1, l8, respectively, to which the open ends of the respective bellows I9, 20 are fixedly connected as by soldering. Each of the transverse abutment members l'L 'ltincludes a chamber 2| in communication with the bellows, asillustrated in Fig. 2. The

closed ends of the respective bellows engage and transmit force to an actuated cross member or bar-122 which carries a-pair of parallel rods 23 c'onnectingtogether a-pair of opposed cross heads 24, 2t i ;'rne be11owsr':o is of somewhat greater, capacity "Ethan the bellows l9 and acts in opposition there- 1 to,being aided in this action by coil compression "springs 26 which encircle depending guide mem 21 while the paral- Each of the oppositely acting valves I5 includes a valve member which is spring urged to closing position relative to a valve opening or seat,

as illustrated in'Fig. 2, and having a tappet stem portion 40 which is adapted to be engaged the cross heads 2|, 25 respectively upon vertical movement of the latter, to open the valves and permit flow of fluid to or frorn th'e drying element l as thecase may be, in the direction of thearrows in A closed boiler or vessel Fig. l. 7

3|. which is partially filled with a quantity of volatile liquid 3H1 such asfacetone-having' alow boil ng point is secured to the downturnedend 9 of the siphon discharge landa v vesselthrough the siphon discharge'tothech'amtubefllea'ds from the interior of this bet 2| at the upper end of smaller bellows it, so

that thevapor pressure generated in the .tube by the expansion of vapor generated from thevolaztile liquid is transmittedto thebellows I! to actuate the same inopposition to the force of springsand the lowermost and larger bellows 10. Such actuation causes the-actuated member 21 to move vertically in either direction an amount proportionalto ;the difference in temperatureof the vapor in the boiler and the dey sired temperature at the. peripheryof drier I,

- with resultant actuationzof one or the other of the valvetappetportionsifl and opening of the 5 corresponding valve 29 when this difference exceeds a'predetermin'ednumberof degrees.

Dalton's law of partial, pressures states that the temperature can be ascertainedfrom any standard steam table. If, however, air is mixed with steam at a given pressure, its presence reduces the temperature of the mixture in proportion to the'amoiint of air present. Therefore, if air is present in a drying cylinder along with water-vapor;;the temperature is that due only to. the partial pressure of the vapor, while the total pressure is that due to the pressure of the vapor plus. that due to the air present. Thus. for example, if the total pressure exerted against the walls of a vessel is 29.4 lbs. absolute and half this pressure is due to air and half due to saturated steam, the temperature of this mixture will correspond to the temperature of water vapor at 14.7 lbs, absolute, or 212 F. If the proportion of the. air is'increased, the temperature of the mixture will be lowered.

If the medium exerting the'total'pres'sure of 29.4 lbs. absolute had been pure steam instead of a mixture of steam and air, thetemp'crature would have been about 250 F. instead of 212 the percentage of "to or below 212 F. Hence, if steam is used in the drier, the pressure must be F. From the foregoing,

it is evident that temperatures of a mixture of air and steam may be controlled by controlling air present-in the mixture. In a drying cylinder drained through a siphon pipe, itfis often necessary-to carry temperatures pure saturated atmospheric. or less to obtain temperatures at or below 212 F. This is often done, i. e., reduction of the pressure to, atmospheric or below to re- -..ment using steam .as

i atthe same time uadjusting and controlling such temperatures, I

duce the temperature suitably;

vacuum, due to the however, in order to effect drainage of condensate from the drier, a vacuum pumpmust be used and it follows that the lowest practicaltemperature attainable depends on the maximum vacuum which is economical to carry by means of a pump or condenser and pump. The installation and operation of such a systemisexpensive, both from'the standpoint of first cost and maintenance and 'in actual practice it is difiicult, to accurately maintain'low temperatures within a drying cylinder under fact that the high vacuum necessary for drainage pulls air into the cylinder through the steam "joints and dilutes the steam by. an uncontrollable amount, with'resulting unpredictable variations in temperature.

Accordingly, in order to provide a means for accurately maintaining low temperatures in (or in any heat transfer equipthe heating medium) and provide means for accurately drying cylinders have produced the above described device and a brief description will make evident its manner, of functioning to these ends.

, Assuming that it is vdesired'to maintain a temperature.of.F. withinthe drier I, it is readily ascertainable that the pure steam pressure corresponding to this temperature is 3.714

. lbs. absolute, which corresponds toa vacuum of 22.35. inches of mercury. However, in order to cause condensate to flow out of the drier through siphon pipe sufllcient pressure must be carried in the drier to lift the condensate up over the siphon and for sake of illustration it may be assumed that this pressure is 3 lbs. gauge tube l2.

perature.

or 17.7 lbs. absolute. In order to assure that j steam will flow from the supply header through pipe 2 to the'd'ri'er, the steam supply pressure is maintained constant by regulator 4' at 3 lbs. gauge.

If the drier has just been started after a period of inactivity during which time ithas filled with air'through leaks around the steam" joint and by back flow through trap I4, the temperature'of the interior of the drier corresponds to atmospheric temperature. A steam is turnedinto the drier, thetemperature rises and heat is transferred through the walls of boiler 3|, which heat raises the temperature of the volatile liquid within the boiler and sets up 'is transferred through small tube 32 to bellows I9, setting up a corresponding force against actuated member 22. The controldevice will be adjusted whereby the force exerted by springs '26 plus that exertedby bellows 20 just balances the force exerted by bellows [9 when the drier reaches 150F. When these forces balance, ac-

tuated member 22 is in neutral position and both valves 29 are spring pressed to closing position so that no air is admitted through the tube 5 and no steam-air mixture exhausted through Under theforegoing conditions, the total pressure within the drier will be 3 lbs. gauge or 17.7.lbs. absolute and of this 3.714 lbs. absolute will be due to steam while 13.986 lbs. will be due to air. p 7

Now assume that the temperature within the drier I rises about 150 F. Thi means that the partial pressure due to the steam has become a greater percentage. of .the total pressure and as a result the vapor pressure exerted by the volatile liquid in. the boiler 3| increases to overbalance the combined opposing, forces in springs 28 and bellows 20. ,When, as a result of this .overbalancing, the cross head 25 engagesthe lowermost valve tappet 30' and unseats the corresponding valve, compressed air willbe admitted throu h tube or line 5 to drier I, thereby increasing the partial pressure in the drier due to .air and decreasing that due to steam. As a result, the temperature within the drier will be reduced and will continue to fall until 150 F, is again reached, atwhich time the forces due to springs and bellows will again be in equilibrium and the actuated member 22 will return toneutral position with both valves 6, l5 shut off. If the temperature in the drier falls below 120 the operation is reversed, i.- e., the vapor pressure in the boiler 3| is lowered, with corresponding reduction in the force exerted'by bellows l9 and valve I5 is opened to exhaust steam and air mixture. The air pressure lost by such venting is replaced by steam from pipe 2, with the resulting temperature raise and restoration of equilibrium. v

In considering the above operation, it should tremely low to the temperature corresponding to the maximum steam pressure available.

.It willbe apparent to thoseskilled in the art that the .entire force opposing. bellows 19 could be supplied bysuitable springs 26, however I have provided the bellows 20 in order to enable a remote control of a numberof drying cylinders,

such remote controlenabling the temperatures in all the driers to be simultaneously adjusted while at the same time maintaining any desired difference or gradation in :the temperatures of a the various individual" driers.

This obviously greatly-facilitates the adjustment ofthe'driers for different jobs; Were some such provision not present, it would'be necessary to individually "adjust the nuts 28 controlling the compression of.

springs 26 for each of the driers, a tedious, inaccurate, and time consuming operation. '1 The mechanism for performing the aforesaid simultaneous adjustment consists of a source of fluid pressurewhich may be air. waterioil, or any other suitable medium, the said medium be- 'ing supplied to a header 33 connected by branch tubes 34 with the corresponding control chambers 2| provided on each of the lowermost bellows abutment members I8. A supply of the medium is controlled by a suitable valve' 35 and it will be apparent that by admittingmore of the air or other medium to the bellows 20, it is possible to regulate the force exerted thereby in opposition to the bellows l9. Y

I find the use of a boiler 3| and a volatile liquid whose vapor pressure is effective on bellows 9 tion.

to be of particular value in the interests of ,ac-

curacy of operation of the control of myinven- Thus, I have observed that the air and steam mixture within. the cylinder tends 1 to stratify in temperature, being cooler immediately adjacent the cylinder periphery. where the work is done and hotter adjacent the center of the cylinder. Of course, it is the temperature immedi ately adjacent the periphery of the cylinder through the downturned end 9 of the siphon disbe kept in mind that the total drier pressure remains constant and that partial pressures due to air and steam are varied to control drier tem- I have found in actual installation of the foregoing system that'the temperatures-with charge 8 the niixture would be heated above its temperature immediately adjacent the drum, with the result that the mixture effective on the control device would not be at a pressure corresponding to its true temperature adjacent the drier periphery. Consequently, the resultant adjustment or regulation would be inadequate. To overcome this and provide assurance that at all times the pressure effective bn bellows l9 wiil accurately reflect the temperature condition immediately adjacent the periphery of drier i, I employ the boiler 3| and connections which have been described above and I find that it performs faithfully in response to changes in that temperature. i

In Figs. 5 and 6, I illustrate a modified em" bodiment of my invention. This-consists of a diaphragm chamber 36 with which tube 32 communicates, the pressure transmitted therethrough being effective on a diaphragm 31 .v This diaphragm acts directly on a plunger-38 which is secured to a cross head 39, urged upwardly by coil springs 40 in opposition to the fluid force exerted on the diaphragm, Plunger 28 carries in the drier l' may be controlled to very close limits of variation and that any temperature can be maintained, from that corresponding to' ex- .a pair of depending rods 4! to which. are secured a pair of spaced parallel cross bars 42 each havthe .alined oppositely acting vertically reciprocable'valve stems. 'These'stemsare connected respectively to needle valves l5, l6 controlling the valves I and 6, respectively, and thereby governing the inflow of air through connection 5 and the exhaust of steam through. tube-.112. The said valve stems 44 are yieldabl-y connected by a coil spring 41. abutting cupped sheet metal.

thrust; members ll attached to the respective stems. It will be noted that the vertical spacing of cross bars 42 is greater than the normal distance between the thrust members 4| when the spring 41 is in relaxed position. i

The diaphragm housing or chamber '36 is fixedly supported by suitable frame members. "49 and if desired the pressure therein may bereadily ascertained from a suitable gauge 50 whereby it is possible to ascertain the temperature of the! volatile liquid in bo'iler SI and thus the temperature in the drier adjacent its periphery. If-desired, this device may be directly calibrated in terms of temperature;

amaz -131' drops below :a predetermined point and air :ad- .mitting; air to the drier member whensaidptemperature rises above a' predetermined point, com- .prising-fialined: az'opposite'ly acting valves eoonla'olfling said .supply and 'said steam and air exhaust connections, a diaphragm housing, a diaphragm therein, a boiler. element associated with said siphon tube. in said drier .member adjacent the periphery of'the lattensaid boiler element containing 'a -;thermally responsive :fluid having a relativelyylow boiling. point, means for communicating saidboiler with saidldiaphragm housing to one sideoi-the diaphragm whereby changes in the temper-ature of the boiler producepro- The operation of the foregoing device isgensteam exhaust tube I! while increase in temperature above the desired point causes an opposite operation, i. .e., opening of the air inlet connection 5.-

The aforesaid system is one which is extremely accurate in its operation to maintain at all times.

a balance of steam and air in the drum sufficient to preserve the desiredtemperature without the need for expensive vacuum pumps or other apparatus and without errors due to stratification as discussed above.

temperatures and it has a wide adaptation to paper web drier" controls, slasher machines; and other common types of drying 'ins'trumentalities as well as to other types'of heat exchange 'units.

I have illustrated and described my improvements in embodiments which are very practical.

I have not attempted to illustrate or describe other embodiments or adaptations as it is believed this disclosure will enable those skilled inthe art to'embody or adaptmy improvements as may be desired. I

Having thus described my invention, what I It. is well adapted for the x control of a number of drier units at graduated portionate changes .in...the pressure on the. ritephragm, and means "for connecting said diaphragm w-ith.rsaid valves for actuation thereof in response to movement of the diaphragm, said meansincluding .a flexible connection for the valves, and a. spring actingon said diaphragm in opposition to the'vapor pressure thereon, said valves opening the :air supply connection and closing the air-steam connection and vice versa, upon movement of the diaphragm in opposite directions, said flexible connection 1118 both i valves tojclos'ing position in neutral position of the diaphragm-. 1

2. "A temperature control for a heat exchange member, comprising means for supplying steam tosaid member, a connection for supplying air to the member, means for exhausting condensagtionwand .a relatively ,cool mixture of air and steam from apoint within the member adjacent the radiating surface thereof, comprising-m c:- haust connection andfla siphon tube in communication therewith, said .tube having an offset end' termlnating closely adjacent the radiating surface whereby. to remove the mixture under 0 the influence of the pressure in the member,

and means to control the exhaust from the heat exchange member when its temperature adjacent the radiating surface drops below a predetermined point and for admitting air to the heat exchange member when said temperature rises above apredeter'mined point, comprising valves controlling said air supply and said steam and air exhaust connections'ja' diaphragm housing,-

claim'as new and desire to secureby letters Patent is: 1

1. A temperature control for a cylindrical r0- tating heat exchange member, comprising means for supplying steam to said member atconstant pressure, a connection for supplying air to the cylinder at a pressure slightly in excess of the pressure of the steam supplied thereto, means for exhausting condensation and a relatively cool mixture of air and steam from a .point within the member adjacent the periphery thereof; comprising an exhaust connection and a siphon tube in communication therewith and extending axially of the member, said tube having an offset and terminating closely adjacent said periphery whereby to remove the mixture under the influence of the pressure inthe cylinder, means to control the exhaust from the drier member when its temperature adjacent the periphery a diaphragm therein, a boiler element associated withsaid siphon'tube in said member adjacent the surface of the latter, said'boiler' element 'con-.

taining a thermally expansive fluid having a relatively low boiling point, 'means for communicating said boiler with said diaphragm housing to one side of the diaphragm whereby changes in the temperature of the boiler produce proportionatechanges in the pressure on the diaphragm, and: means for connecting said diaphragm with .said valves for actuation thereof in response to movement .of the diaphragm, said valves opening the airsupply connection and closing the air-stream exhaust connection and vice versa upon movement of' the' diaphragm in opposite directions.

3. -In a temperature regulator for a heat exchange unit, means'for supplying heating steam to said-unit, an air supply connection to mix air with steam supplied to the unit and a connection forexhausting relativelycool steam and air from the unit, comprising a siphon discharge extending immediately adjacent the radiating surface of the unit, valve'means for said connections for. simultaneously opening one thereof andclosing the other and vice versa, and means for actuating said valve means in response to.

variations in temperature immediately adjacent said surface, comprising a pressure responsive member, and means for applying pressure on said .member proportional to the temperature in said unit adjacent its surface, comprising a boiler element disposed in said'unit adjacent the surface and containing a fluid having a boiling point lower than the normal temperature adjacent said surface and a tube'for communicating fluid in said boiler element 'with'said pressure responsive member to act on the latter whereby the pressure exerted thereon is directly proportionalc. to the temperature of said boiler, and means for actuating said valve means from said pressure responsive member, whereby upon movement thereof in either direction from a neutral point one of .the connections is opened and the other closed, both thereof being closed by the valve means in said neutral position.

4. In a temperature regulator for a heat exchange unit, means forsupplying heating steam to said unit,-an. air supply connection to mix air with steam supplied to the unit and a connection for exhausting relatively cool steam and air from the unit, comprising a siphon discharge extending therein, valve means for said connections for simultaneously opening one thereof and closing the other and vice versa, and means for actuating said valve means in response to variations in temperature in the unit, comprising a pressure responsive member, and means for-applying pressure to said last named member proportional to the temperature in said heat exchange unit, comprising a boiler element disposed in the unit and containing a liquid having a relatively low boiling point and a tube for communicatingvapor pressure in said boiler element with said pressure responsive member whereby the pressure exerted thereon is proportional to the temperature of said boiler, and means for actuating said valve means from said pressure responsive member whereby upon movement of the latter in either direction one of the connections is opened and the other closed.

5. A temperature control for a low pressure heating member to maintain the temperature adjacent a heating surface thereof at a predetermined point, comprising means for supplying steam to said member, a connection for supplying air thereto and a further connection for exhausting steam and air therefrom, said connections having valves therein, and means for actuating said valves to admit air to the member from said first named connectionwhen the temperature adjacent said surface rises above a predetermined point -and to exhaust steam and air through said second named connection when the temperature drops below a predetermined point, said steam supply means providing steam to take its place, comprising a pressure responsive member for controlling the movement of said valves, and thermally responsive means disposed in said heating member adjacent the heating surface thereof, and communicating with said pressure responsive member to exert a pressure thereon proportional to the temperature adjacent said heating surface.

6. A temperature control for a low pressure heating member to maintain the temperature adjacent a heating surface thereof 7 at a predetermined point, comprising means for supplying steam to said member, a connection for supplying air thereto and a further connection for exhausting steam and air therefrom, valve means controlling said connections, and means for actuating said valve means to admit air to the member from said first named connection when the temperature adjacent said surface rises above a predetermined point and to exhaust steam and air through said second named connection when the temperature drops below a predetermined point, said steam supply means providing steam to take its place, comprising a pressure respon sive member connected to and controlling said valve means, and thermally responsive pressure generating means disposed in said heating member adjacent the heating surface thereof, and communicating with said pressure responsive member including a' connection for transmitting pressure from said'thermally responsive means to said pressure responsive member to exert a pressure thereon proportional to the temperature adjacent said heating surface.

'7. A temperature control for a heating member to maintain the temperature thereof at a predetermined point, comprising means for supplying steam to said member, a connection for supplying air thereto and a further connection for exhausting steam and air therefrom, valve means controlling said connections, and means for actuating said valve means to admit air to the member from said first named connection when the temperature in said member rises above a predetermined'point and to exhaust steam and air through said second-named connection when the temperature drops below a predetermined point, said steam supply means providing steam I to take its place, comprisinga pressure IESPOD:

provided with a return check valve for supplying" steam to said cylinder at a predetermined pressure, a siphon tube exhaust connection for said cylinder, a steam trap to which said exhaust connection delivers, an air exhaust valve for said exhaust connection disposed in advance of said trap, an air supply connection delivering to said steam supply connection at the rear of its said check valve, an air inlet valve for said air inlet connection, an operating connection for said air inlet and said exhaust valve including springmeans acting to normally close both valves;'a control means for said valves comprising/a pressure chamber, a boiler element disposed in said cylinder adjacent the periphery ,thereof, said boiler element being connected to said pressure chamber by a tube arranged through said siphon tube, a pressure actuated member operatively associated with said pressure chamber and with said valves for opening the air inlet valve when the pressure exceeds a, predeterminedpoint, and spring means acting in opposition to said pressure actuated member for closing the air valve and opening the exhaust valve when the pres sure in said pressure chamber falls below a predetermined point.

9. A temperature control for a steam drier having a source of steam communicating therewith, comprising means-for supplying'air to said drier for mixture with steam supplied thereto, means for exhausting steam and air from said drier, valve means controlling said air supply and exhausting means respectively, and means for actuating said valves to admit air to said drier when the temperature therein rises above a predetermined desired point and for exhausting steam and air from the drier when the temperature thereof falls below a predetermined point, whereby steam from said steam supply means raises .the temperature, comprising a vessel disposed in said drier adjacent the periphery thereof, said. vessel containing a volatiieliquid adapted to generate vapor pressure when heated, a pressure responsive element. means for actuating said valve means from said pressure responsive element, and means connecting said pressure responsive element with said vessel whereby .said vapor pressure is eifective on said element to actuatethe same.

10, A control for steam heated driers and the like having steam supply means connected thereto, said control including means (or drainingcondensate from the drier, means for supplying air totheinteriorot the drier, means to! exhausting air and steam from the interior of the drier, valve means for, controlling said air supply and exhaust means, mean for actuating said valve means in'accordance with the temperature within the drier, comprising a thermally responsive element in the drier having a volatil liquid therein adapted to generate vapor pressure in accordance with the variations in temperature or the drier, a flexible bellows communicating with said element and subject to said vapor pressure, means connected to and actuated by said bellows for actuating said valve means. and resilient means for opposing movement or said bellows in one direction including a further pressure responsive element opposing said bellows,and means for varying the force exerted by said last named pressure responsive element.

ll. A control as: steam heated driers and the like having steam supply means connected thereto, said control including mean (or draining condensate from the drier, means for simplying air to the interior or the drier, means !or exhausting air and steam from-the interior or the drier, valve-means for controlling said air supply and exhaust means, means for actuating said valve means in accordance with the temperature within the drier, comprising a thermally responsive element in thedrier having a volatile liquid therein adapted t Generate vapor pressure in accordance with the variations in temperature or the drier, a flexible bellows communicating with said element and subject to said vapor pressure, and means connected to and actuated by said bellows for actuating said valve means.

12. In an apparatus of the class described, the combination of a drier cylinder, 9.. connection for supplying steam to said cylinder at predetermined pressure, a siphon exhaust tube connected to said cylinder, an air exhaust valve for said exhaust .tube, an,air supply pipe connected to said cylinder, an air inlet valve for said air supply pipe, an operatingconnection in said air inlet and said exhaust valves includin a spring means acting to normally close both valves. a control means for said valves comprising a pressure chamber, a boiler element disposed in said cylinder adjacent the periphery thereof. said boiler element being connected to said pressure chamber by a-tube arranged through said siphon exhaust' tube, a pressure actuated member oper-, atively associated with said pressure chamber and with said valves for opening the air inlet valve when the pressure within said boiler element exceeds a predetermined point, and spring means acting in opposition to said pressure actuated member for closing the air valve and opening the exhaust vaivewhcn the pressure in said pressure chamber falls below a predetermined point.

13. In an apparatus of the class described, the combination with a heat exchange element having a radiating wall, ola connection provided with a return check valve for supplyin steam to said element at. predetermined pressure, a siphon exhaust tube connected to.said element,

a steam trapto which said exhaust tube delivers,

'elementbeingoonnectsdtosaidprcssurechamberbyatubcarrsngcdtbroughsaidsiphonexhaust tube, a pressure actuated member operatively associated with said pressure chamber and said valves for opening the air inlet valve when the pressure within said boiler element exceeds a predetermined point, and spring means'acting in opposition to said pressure actuated member for closing the air valve and opening the exhaust valve when the pressure in the pressure chamber atslls below a predetermined point.

14. In an apparatus of the class described. the combination with a heat exchange element'having a radiating wall, ota connection for supplying steam to said element at predetermined pres sure, an exhaust tube connected to said element, an air exhaust valve in said-exhaust tube, an air supply pipeconnectedtosaldclementhavingan air inlet valve therein, an operating connection iorssidairinletandsaldcxhaustvalvesincludingsspringmeansactlngtcnormallycloscboth valves, a control means (or said valves comprising a pressure chamber, a boiler element disposed in said heat exchange element adjacent the radiatingwall thereof, said boiler element being connected to'said pressure chamber by a tube arranged through said exhaust tube, a pressure actuated member operatively associated with said pressure chamber and said valves for opening the airinlet valve when the pressure within said boiler element exceeds a predetermined point, and spring means acting in-opposition to said pressure actuated member for closing the air valve and opening the exhaust valve when the pressurein the pressure chamber falls below a predetermined point.

15. In an apparatus of the class described, the combination with a heat exchange element having a radiating wall, of a connection provided with a return check valve for supplying steam to said element at predetermined pressure, a siphon exhaust tube connected to said element, a steam trap to which said exhaust tube delivers, an air exhaust valve in said exhaust tube disposed in advance of said trap, an air supply pipe connected to said steam supply connection at the rear of its said check valve, an air inlet valve insaid air supply pipe, a control means for said valves including a pressure actuated element, and a boiler element disposed in said heat exchange element adjacent the radiating wall thereof and operatively associated with said pressure actuated element, a shiitable member operatively associated with said pressure actuated element and said valves for opening the air inletvalve when the boilerpressure on said last named element exceeds a predetermined point, and spring means acting on said shiftable member for closing the air valve and opening the exhaust valve when the boiler pressure on the pressure actuated element falls below a predetermined point. I

16. In an apparatus of the class described, the

combination with a heat exchange'element having a radiating wall, of a connection for supplying steam to said element at predetermined pressure, an-exhaust tube connected to said element, a steamtrap to which said exhaust tube delivers, an air exhaust valve in said exhaust tube, an air supply pipe connected to saidheat exchange element, an air inlet valve in said air supply pipe, acontrol means for said valves including a pressure actuated element, and a boiler element disposed in said heat exchange element: adjacent the radiating wall thereof and operatively associated with said pressure actuated element, a shiftable'member operatively associated with" said pressure actuated element and said valves for opening the air inlet valve when the boiler pressure on said last named element exceeds a predetermined point, and spring means acting on said shiftable member for closing the air valve and opening the exhaust valve when the boiler pressure on the pressure actuated element falls below a predetermined point.

17. A control for steam heated driers and the like having steam supply means connected thereto, said control including means for draining condensate from the drier, means for supplying air to the interior of the drier, means for exhausting air and steam from the interior of the drier, valve means forcontrolling said air supply and exhaust means, means for actuating said valve means in accordance with the temperature within the drier, comprising a thermally responsive element in the drier having a volatile liquid therein adapted to generate vapor pressure in accordance with the variations in temperature of the drier, pressure responsive means com,- municating with said element and subject to said vapor pressure,'means connected to and actuated by said pressure responsive means for actuating said valve means, and resilient means for opposing movementpf said pressure responsive means in one direction including a further pressure responsive element opposing said first named pressure responsive element, and means for varying the force exerted by said last named pressure responsive element.

18. A control for steam heated driers and the like having steam supply means connected thereto, said control including means for draining condensate from the drier, means for supplying air to the interior of the drier, means for exhausting air and steam from the interior ofthe drier, valve means for controlling said air supply and exhaust means, means for actuating said valve means in accordance with the temperature within the drier, comprising a thermally responsive element in the drier having a volatile liquid therein adapted to generate vapor pressure in accordance with the variations'in temperature of the drier, pressure responsive means communicating with said element and subject to said vapor pressure, and means connected to and actuated by said pressure responsive means for actuating said valve means.

19. A control for a drying system including a plurality of driers arranged in series and having means for supplying heating medium thereto, said control comprising a plurality of temperature responsive elements containing a volatile liquid, a plurality of pressure responsive elements connectedto and subject to vapor pressure arising in said first named elements due to variations in temperature of the driers, there being a pressureresponsive and a thermally re-- sponsive element for each ofv said driers, the latter being located internally .or the driers,

means connected to said driers for supplying and exhausting heating medium therefor including intake and exhaust valves, means controlled by said pressure responsive elements/for actuating said valves, and resilient means acting in opposition to said pressure responsive elements, comprising a pluralityof bellows one for each of said driers, each ofsaid bellows acting in'opposition to the force exerted by said first named pressure responsive elements, and means for simultaneously regulating the force exerted by said bellows, comprising a'source' of fluid exhaust valves, means controlled by said bellows for actuating said valves, separately adjustable spring thrust means for said bellows, a bellows acting in thrusting opposition to each of said first named bellows, a common source of fluid control medium for said second bellows, and means for controlling said fluid medium.

21. The combination with a plurality of heat exchange units, of a common heating fluid supply for said units, a temperature responsive element containing a volatile liquid operatively associated internally of each unit, a pressure responsive bellows connected with each of said temperature responsive elements, means connected to said units for supplying and exhausting heating medium therefor, including intake and exhaust valves, means controlled by said pressure responsive elements for actuating said valves, a bellows acting in thrusting opposition to each of said first named bellows, a common source of fluid control medium for said second bellows, and means for controlling said fluid medium.

22. The combination with a plurality of heat exchange units, of a common heating fluid supply for said units, a temperature responsive 'element containing a volatile liquid operatively associated internally of each unit, a pressure responsive element connected to each of said temperature responsive elements and subject to variations in pressure therein resulting from variations in temperature of the heat exchange unit with.

which its temperature responsive element is associated, means connected to said units for supplying and exhausting heating medium therefor. including intake and exhaust valves, means controlled by said pressure responsive elements for actuating said valves, separately adjustable ply for said units, a temperature responsive-element containing a volatile liquid operatively associated internally of each unit, a pressure responsive'element connected to each of said temperature responsive elements and subject to variations in pressure therein resulting from .variations in temperature of the heat exchange unit with which its temperature responsive element is associated. means connected to said "units for supplying and exhausting heating medium therefor, including intake and exhaust valves, means controlled by said pressure responsive elements for actuating said valves, a belxlowsacting in thrusting opposition to each of said-pressure responsive elements, a common source of fluid control medium for said bellows. and;means for controlling said fluid medium.

24. The combination with a plurality of heat exchange units, of a common heating fluid supply for said-units, a temperature responsive element containing a volatile liquid operatively associated internally of each unit, a pressure responsive element connected to each of said temperature, responsive elements and subject to variations in pressure therein resulting from variations in temperature of the heat exchange unit with which its temperature responsive element is associated, means connected to said units for supplying and exhausting heating medium therefor,- including intake and exhaust valves,

means controlled by 'said pressure responsive elements for actuating said valves, separately justable spring thrust means for said pressure responsive elements, a pneumatic thrust means in thrusting opposition to each of said pressure responsive elements, a common source of fluid control medium for said pneumatic thrust means. and means for controlling said fluid medium.

' ADAM E. ARMSTRONG. 

